I am trying to get an NOS Duraplane 40 with ailerons flying and have problems some because over the years lost the instructions and or plans to it but maybe someone can help?

it seems to very clumsily balance on a CG 1/3 back from the front edge of the wing it won't stay suspended in air but teeters to one end or the other not always one end like it heavy on one end.
From what I can find these are know to be really bad ground handlers and mine is no exception crashing on it's maiden take off never leaving the ground! Some have converted to a tail dagger others adding wing tip skids or both. My thinking from observation is: poor balance on the main gear :meaning the nose wheel comes off the ground with the slightest touch of the tail , so the nose grear /wheel is not biting in .
So why not move the main gear back until the nose gear / wheel gets a good bite ? That leads to how far back can I go ? this is an albatross for sure and will never be a good balanced flying machine so I'm trying for what will work and avoid crashes especially when pulling the throttle back to taxi and take off and it just flops over, very embarrassing !


Thanks for any help
Jayd